In a normal electronic product such as a computer, electronic devices will generate a lot of heat during operation. If the electronic devices are continuously operated at high temperature, they are easily damaged. Thus, to prevent such a damage, a heat-dissipating fan is normally disposed in the electronic product to dissipate heat to the surrounding.
Please refer to FIG. 1 which shows a conventional axial-flow fan for the computer. The conventional axial-flow fan mainly includes a housing 10, a motor 11 and an impeller 12 with a plurality of blades. The housing 10 includes a base 14 for supporting the motor 11 and has a plurality of ribs or stationary blades 13 at the air outlet side of the axial-flow fan. When the motor 11 drives the impeller 12 to rotate, the blades 121 will discharge the airflow from the air outlet side of the axial-flow fan. However, each upper edge of the ribs or stationary blades 13 is shaped in a horizontal form so that the airflow generated by the blades 121 will arrive at the ribs or stationary blades 13 at the same time. Furthermore, the distance H between the lower edge of the blade 121 and the upper edge of the rib or stationary blade 13 is relatively small such that it will cause a lot of noise in a very short time as the airflow passes therethrough and worsen the sound, resulting from the air turbulence.
Thus, it is desirable to reduce the air turbulence noise of the axial-flow fan generated while rotating.